To install RPMforge repo in yum,

http://wiki.centos.org/AdditionalResources/Repositories/RPMForge

#wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm
#rpm –import http://apt.sw.be/RPM-GPG-KEY.dag.txt
#rpm -K rpmforge-release-0.5.2-2.el5.rf.*.rpm

#rpm -i rpmforge-release-0.5.2-2.el5.rf.i386.rpm